Connect the acceptor
The acceptor runs on about 12 V and signals by pulling a wire to ground. A diode on each signal line lets that low through and keeps everything higher out, so the pulse reaches your pin at your board's own voltage.
Four pins
The acceptor socket at the bottom of the mainboard prints its four positions: COUNTER, GND, COIN, +12V, with an arrow at COUNTER. The kit's four-wire cable goes from there to the acceptor's own socket. With everything unplugged, fit it at both ends, then power the mainboard from its USB-C.
+12V is an output. The mainboard makes it for the acceptor, and nothing else in the kit may touch it.
A 12 V machine on a 3.3 V pin
The acceptor never drives its signal wire high. For each pulse it switches the wire to ground, and between pulses it lets go. What the wire rests at when it is let go is the acceptor's business, and on a 12 V machine it can be 12 V.
So the mainboard puts a diode in the way: D6 on COIN, D5 on COUNTER, both SS24 Schottky diodes. A diode passes current one way only. When the acceptor pulls low, current flows from your board's side through the diode into the acceptor and the pin drops to a few tenths of a volt. When the acceptor lets go, nothing can flow back the other way, and a 10 kΩ resistor to V(MCU) holds the pin at your board's own voltage.
That is why the lines idle HIGH and pulse LOW, the opposite of the buttons, and why the code watches for a falling edge on them.
COIN and COUNTER
The acceptor has two signal outputs and the mainboard wires both through to the header: COIN on position 19, COUNTER on position 18. On most acceptors with these two, COIN sends several pulses whose count says which coin it was, and COUNTER sends one pulse per coin, for a mechanical counter.
The kit's examples read COIN. The ESP32-S3 and Zero 2 W probes watch COUNTER as well, so you can see what your acceptor sends on each before you choose.
Teach it the coins
A new acceptor recognises nothing. Teaching it means feeding it samples of each coin and setting how many pulses each should send, with the buttons and display on the acceptor itself. The sequence differs between models, so use the manual that came with yours. Set one coin to one pulse to begin with: it is the easiest thing to recognise in the probe.
When it does not work
It has to be taught the coins first, with the buttons on its own side, following the manual that came with it. Until then it treats every coin as unknown and drops it into the return chute, which looks exactly like a fault.
It has no 12 V. Plug the mainboard's USB-C in: the development board's USB does not power the acceptor. Then check the four-wire cable is fully home at both ends.
Not into the USB-C socket and not into any header pin. The mainboard makes its own 12 V from 5 V and puts it on the acceptor socket only. Feed the USB-C socket 5 V and nothing else.
Go by the labels, not the colours. The mainboard prints COUNTER, GND, COIN, +12V beside the socket, left to right with the arrow at COUNTER. A replacement cable can carry any colours at all.
Why one coin arrives as a burst, and how the probe puts the burst back together.
Count the pulses →Edit this page — content/books/arcade/connect-the-acceptor.mdx
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HotSwap Arcade Kit: Buttons, Joystick and Coin Acceptor for ESP32-S3, Nano, Pico and Zero 2 W
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